Trouble parameterizing components

[JetForMe]

I'm having trouble figuring out how to model and assemble a series of components such that a number of dimensions are parameterized. Here's the work-in-progress:

 

The two hanging flat pieces are linked components. The horizontal flat piece is a separate component (which will eventually have a linked pair on the opposite side). I want to parameterize the widths and lengths of everything separately, but I want the three pieces to be assembled together in a rigid assembly, and stay that way despite parameter changes.

Moreover, I want them to remain centered on the origin.

There is a revolute joint between the hanging pieces and the axle. The axle is currently grounded. I had tried to make the second hanging component with a parameterized move, but it seems I can't get back to edit that move.

Should those plates be bodies of one component, instead? What's the best way to specify the overall width, and have the cross plate grow and shrink, but always stay attached to the hanging plates?

Thanks!

[daniel_lyall]

How I would do it is put the origin to good use.

First part the rod draw it on the origin then extrude from there useing symmetric with a paramater, then put a rigid joint between the rod and origin.

Do a offset plane from the origin for the second part of it's origin in it's own component use the paramater you have already set up for it then sketch the part on the plane do a mirror of the part useing the origin. Doing this if you wont both to stay at a equal distances from each other you change the paramater they all move together.

If you wont post what you have done so far

Example attached